title: Ionotropic glutamate receptors IR64a and IR8a form a functional odorant receptor complex in vivo in Drosophila.
abstract: Drosophila olfactory sensory neurons express either odorant receptors or ionotropic glutamate receptors (IRs). The sensory neurons that express IR64a, a member of the IR family, send axonal projections to either the DC4 or DP1m glomeruli in the antennal lobe. DC4 neurons respond specifically to acids/protons, whereas DP1m neurons respond to a broad spectrum of odorants. The molecular composition of IR64a-containing receptor complexes in either DC4 or DP1m neurons is not known, however. Here, we immunoprecipitated the IR64a protein from lysates of fly antennal tissue and identified IR8a as a receptor subunit physically associated with IR64a by mass spectrometry. IR8a mutants and flies in which IR8a was knocked down by RNAi in IR64a+ neurons exhibited defects in acid-evoked physiological and behavioral responses. Furthermore, we found that the loss of IR8a caused a significant reduction in IR64a protein levels. When expressed in Xenopus oocytes, IR64a and IR8a formed a functional ion channel that allowed ligand-evoked cation currents. These findings provide direct evidence that IR8a is a subunit that forms a functional olfactory receptor with IR64a in vivo to mediate odor detection.
authors.affiliation: Molecular Neurobiology Program, Department of Cell Biology, and Department of Biochemistry and Molecular Pharmacology, Kimmel Center for Biology and Medicine at the Skirball Institute, School of Medicine, New York University, New York, New York 10016, USA.
authors.forename: Minrong
authors.initials: M
authors.lastname: Ai
authors.forename: Steven
authors.initials: S
authors.lastname: Blais
authors.forename: Jin-Yong
authors.initials: JY
authors.lastname: Park
authors.forename: Soohong
authors.initials: S
authors.lastname: Min
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Neubert
authors.forename: Greg S B
authors.initials: GS
authors.lastname: Suh
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001522:Behavior, Animal / Q000502:physiology; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D004330:Drosophila / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D015640:Ion Channel Gating; D007473:Ion Channels / Q000378:metabolism; D018034:Olfactory Receptor Neurons / Q000502:physiology*; D009865:Oocytes / Q000378:metabolism; D058468:Receptors, Ionotropic Glutamate / Q000235:genetics / Q000502:physiology*; D012903:Smell / Q000502:physiology; D014981:Xenopus
chemical_list: D018076:DNA, Complementary; D029721:Drosophila Proteins; C554857:IR64a protein, Drosophila; D007473:Ion Channels; D058468:Receptors, Ionotropic Glutamate; C555766:ionotropic receptor 8a, Drosophila; D049452:Green Fluorescent Proteins; D002118:Calcium